The invention relates generally to a method of operating a press and, more particularly to a method of operating a press wherein a continuously alternating motion of a first die relative to a second die occurs between a first and a second dead center, and wherein means are provided for detecting the pressing force.
Such methods of operating presses are commonly employed with commercial presses. For example, the tripping of a working stroke which occurs either by means of conventional mechanical cam controllers or with the aid of electronic cam controllers is disclosed in German published patent application 35 28 922.
It has been found that with longer production cycles the pressing force fluctuates. These fluctuations may result from either wear on the press such as gradual wear of the dies, or because of differently rolled metal sheets. An operator ascertains that the pressing force is off, that is, becoming too small based on the shape of the pressed parts. Prior to the present invention, it has been the practice to correct the the pressing force was corrected by varying the position of the die. However, observing the work flow does not yield more than a rough estimate of the magnitude of the change in the pressing force. Thus, making repeated adjustments of the position of the die may be necessary to optimize the quality of the workpiece. These repeated adjustments have resulted in a certain expected percentage of rejects.
The present invention is directed to modifying a convention method to maintain an optimum constancy of the pressing force during operation.